As Dave already indicated, the tadpole comparision is to indicate that if millions of tadpoles make the transition from fish-like to tetrapod lifestyles every year, it does not seem like an insurmountable morphological barrier for evolution. Amphibian larvae are not taphonomically durable. Their fossil record is poor, so it's hard to tell to what extent a larval developmental stage was present in the earliest amphibians. I'd guess that the salamanders are probably closer to the ancestral form in that regard, with a less dramtic change than in frogs and toads.
Incidentally, the change from herbivory in tadpoles to carnivory in the adult is probably a reversal of the evolutionary pathway, contrary to a strict Haeckelian model. Carnivory (s.l., including insectivory, etc.) seems to be the primitive condition for most vertebrate groups. Of course, as strict Haeckelian recapitulation (which his modified embryo drawings were intended to support) is contrary to a modern understanding of evolution, it's not surprising that the tadpole doesn't match, either.
Vernon raised the issue of how this fits into an understanding of Genesis 1-3. Although it's an important issue, which has generated plenty of discussion on the list and elsewhere, for the purposes of discussing transitional forms I would simply point out that any interpretation of Genesis 1 leaves the mandates to do good, honest work (e.g., Eph. 6:5-7) unchanged. Whether or not one accepts the reliability of the scientific evidence regarding timing and means of creation, it's important to be careful that claims about the scientific evidence are accurate.
Dr. David Campbell
Old Seashells
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Box 870345
Tuscaloosa, AL 35487-0345 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
Received on Wed Jun 23 18:27:01 2004
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